The present invention relates to a method of producing an antibody to 3-methoxy-4-hydroxyphenylethylene glycol (abbreviated as MHPG hereinafter) which is useful for the measurement of MHPG, an antigen used in the production of the antibody and a method of producing the antigen.
MHPG is a neutral metabolite of norepinephrine and epinephrine, which are adrenal medullary hormones and serve as neurotransmitters of the sympathetic nerve and the central nerve. Measurement of the increase or decrease of MHPG in body fluid is very important for elucidating the transmission function of these information substances.
More particularly, the concentration level of MHPG in the blood or the cerebrospinal fluid is considered to reflect the norepinephrine level in the brain. The measurement of MHPG is also important for the diagnosis of diseases such as melancholia, malignant subarachnoid hemorrhage, and so on, because these diseases are inclined to cause an increase in MHPG levels.
Hitherto, for measuring MHPG levels, gas chromatography, mass spectrometry, high-performance liquid chromatography or the like have been employed. These methods, however, are cumbersome in operation, and only a few specimens can be measured at a time.
Meanwhile, immunological measurement is very capable of rapidly and simply measuring many specimens at a time. This approach, however, requires preparing antibodies and antigens.
A method of preparing an MHPG antigen and an antibody to MHPG has been reported by T. Keeton et al (Science, 211, 586-588, 1981) which comprises reacting 6-bromocaproic acid with MHPG to modify the hydroxyl group at the 4-position of MHPG to --O--(CH.sub.2).sub.5 --COOH, bonding a carrier protein to this carboxyl group via a carbodiimide method to prepare an antigen, and immunizing an animal with the antigen to obtain an antibody.
The thus-formed antibody is not cross-reacted with catecholamine or acid metabolites, but is weakly cross-reacted with 3,4-dihydroxyphenylethylene glycol.